Got Leopard installed on both my Macs. A few minor problems, but they were largely related to networking, and were easily resolved. My initial thoughts: I'm so pleased I spent $129.00 to get some features that have been in Outlook and KDE for years.
I haven't done more than a cursory examination on the masses of audio software installed in my iMac, so I have nothing to add to the conversation there, but everything seems to be okay. I'll edit this post with a full report as I do my testing.
EDIT:
Well, I haven't done a complete and total torture test in all the hosts I have (which is Logic 7, Logic 8, Live 5, Live 6, Cubase SX3, Cubase 4, Plogue Bidule, Tracktion 2, Tracktion 3, DP 5, and all the stupid little ones like GarageBand and Metro and that kind of asshole shit), but in a pretty thorough examination in Live 6, everything seems to work. That picture shows our entire product line on a single channel in Live, with the "About This Mac" window open on top. And boy, it sounds great, too. I think I'll name this song "Motherfuckin' Swamp Thing, Bitch!" Or maybe I'll exit without saving. It's a toss-up.
But everything seems to be fine, at least on the Audio Damage front. Take that as you will.